1. Field of the Invention
This invention relates to improvements in the operation of a fuser in a photocopying machine. More particularly, this invention has a self-recovering feature which lowers the number of paper jams which occur at the fuser and at the cleaner module.
2. Description of the Related Art
In electrophotographic applications such as xerography, a charge retentive surface is electrostatically charged. A light pattern formed from the original image to be reproduced selectively discharges the charge on a retentive surface. The resulting pattern, a combination of charged and discharged areas on the charge retentive surface, form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image area by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being produced. The toner image may then be transferred to a substrate (e.g., paper), and the toner is fused onto the substrate by passing through a fuser. At this point the image is affixed to the substrate and is ejected from the machine to the holding tray. The process is well known, and is useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charged surface may be discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operate similarly.
Occasionally a copy sheet will jam in a variety of places in a xerography machine. In order to reduce the number of paper jams perceived by the operator, it is necessary that certain jam situations be identified and recovered from automatically. This includes fuser misstrips and photoreceptor misstrips. Depending on paper path architecture, each of these jam situations may require the photoreceptor (assumed to be a belt) to stop and back up a short distance so that recovery can take place.
In a copier or a printer, a copy with toned (black) lead edge is known to cause fuser misstrip problems. In addition, copies without a black lead edge often fail to strip from a fuser roll due to toner contamination of the fuser roll, improper fuser oil metering, and aging of the fuser roll surface. In either case, the sheet is held to the roll by the fused toner. If a misstrip occurs the processor paper path shuts down in a hard stop. The operator must intervene, clear the jammed copy and perform any reordering of the original that is required.